Ability of a mixture of antimyotoxin a serum and polyvalent (Crotalidae) antivenin to neutralize myonecrosis, hemorrhage and lethality induced by prairie rattlesnake (Crotalus viridis viridis) venom.

Mixtures containing polyvalent (Crotalidae) antivenin and antimyotoxin a serum were tested for their ability to neutralize the myotoxic, hemorrhagic and lethal activities of crude C. v. viridis venom when mixed with the venom prior to injection into white mice. A light microscopic method was used to measure the local myotoxic activity of the venom, i.e. myonecrosis index. The results show that the neutralizing ability of a 1:1 mixture of antisera for myonecrosis was 16 times that of antimyotoxin a serum alone and 63 times that of antivenin alone. There was no difference in neutralizing ability of the three ratios (2:1, 1:1, 1:2) of antivenin: antimyotoxin serum tested. Hemorrhage was measured by a new method in which the amount of hemoglobin in a muscle extract was measured after i.m. injection of test solution. The results show that the ability of a 1:1 mixture to neutralize hemorrhage was comparable to that of antivenin alone. There was no difference in hemorrhage neutralizing ability of the three ratios tested. In its ability to neutralize lethality, the 1:1 mixture was again comparable to antivenin. However, when the three different ratios of antisera were tested for neutralization of lethality the 2:1 and 1:1 ratios were as effective as antivenin alone, whereas the 1:2 ratio (antivenin: antimyotoxin serum) was less effective than antivenin alone. Thus the addition of antimyotoxin a serum to antivenin in equal proportions greatly improves the neutralization of the myotoxic activity of C. v. viridis venom and does not decrease the ability of antivenin to neutralize hemorrhage and lethality.